In known ignition systems more or less of the kind mentioned above (cf. U.S. Pat. No. Re. 31 837) the inner leg of a three-legged ferromagnetic iron core is surrounded by a coil arrangement. In the latter a pole wheel, which is coupled to the rotating engine shaft and which bears in a peripheral position a tangentially aligned permanent magnet, generates a series of alternating voltage half-waves. The first of these half-waves is used to charge an energy accumulating condenser and only the last half-wave serves for the operation of a thyristor discharging the condenser through the spark coil. In practice, however, it is found that in this method of procedure, the spark is fired always later with respect to the absolute angular position of the magnet pole wheel as the rotary speed increases. Explanations of this phenomenon might lie in the eddy current and hysteresis losses in the polarity reversal of the iron core that precedes the spark firing, and in the encumbrance of the entire ignition system with capacitors and a low-pass filter.